The great artist and inventor Leonardo da Vinci once said that "simplicity is the ultimate sophistication." National Institute of Standards and Technology (NIST) research engineer Javier Atencia certainly believes in the wisdom of what da Vinci preached; he has a reputation for creating novel microfluidic devices out of ordinary, inexpensive components. This time, he has combined a glass slide, plastic sheets and double-sided tape into a "diffusion-based gradient generator" -- a tool to rapidly assess how changing concentrations of specific chemicals affect living cells.